This invention relates to the processing of multi-valued or n-state (non-binary) signals with n>2. More in particular it relates to the scrambling, descrambling, generation and the detection of multi-valued (non-binary) or n-state signals representing sequences of multi-valued (non-binary) or n-state symbols such as n-valued pseudo-noise sequences. Multi-valued signals also referred to as n-valued or n-state signals, can assume one of n states, wherein n is greater than or equal to three.
The n-state scramblers and descramblers are implemented by using a Linear Feedback Shift Register or LFSR. Well known is the binary LFSR based scrambler and the corresponding self synchronizing LFSR based binary descrambler.
Its potential application is in telecommunication systems, control systems and other applications. Specific examples of utility where the invention can be used include spread-spectrum technologies, signal scrambling, CDMA, QAM-2k modulation, multi-state symbol modulation, line-coding and scrambling application in video and other signal modulation and distribution.
LFSR based scramblers are used to change the appearance of a digital signal in such a way that during transmission the signal is different from the original signal. The original signal can be recovered from the scrambled signal at the receiving end by a descrambler. LFSR scramblers are one-to-one coders, coding one symbol on an input to one symbol on an output. LFSR scramblers are commonly used as streaming coders, which are different from word or block coders. Most commonly in today's telecommunications, the scramblers relate to binary signals.
Scrambling of a binary signal can be achieved by combining the binary signal to be scrambled with a second known binary signal through a digital circuit that has the characteristics of a reversible function. A known signal is commonly known as a key and may for instance be derived from a prime number, which may be a large prime number.
In the case of scrambling with an LFSR scrambler there is no real known signal. A second signal that is used for scrambling comes from the LFSR. Such a signal is essentially unknown. However, the nature of the LFSR allows the signal from the LFSR to be reconstructed at the receiving side. Though the signal from the LFSR is still unknown, it can be reconstructed and thus can be applied to recover the original signal from a scrambled signal.
The inventor has provided the rule for an n-valued or n-state LFSR based descrambler corresponding to an n-valued LFSR based scrambler. This has been disclosed in U.S. patent application Ser. No. 10/935,960 filed Sep. 8, 2004 entitled Ternary and multi-valued digital signal scramblers, descramblers and sequence generators and in U.S. patent application Ser. No. 10/912,954 filed Aug. 6, 2004 entitled Ternary and higher multi-valued digital scramblers/descramblers, which are both incorporated herein by reference in their entirety.
There are two known binary functions that can perform this reversible function: the Exclusive Or (XOR) and the Equal or EQUALITY function (=) in a binary scrambler and descrambler. However the XOR function is commonly used exclusively in scramblers and coders. The XOR function is also known as the modulo-2 adding function.
Telecommunication markets such as wireless communications and Internet communications demonstrate an ongoing increase in demand for higher information transmission rates. This demand in increased information transmission rates in wireless communications is addressed by increasing bandwidth of communication channels, by compression of the information and by moving into much higher radio spectra (such as Ultra Wide Band in the 5 GHz area). Eventually, new technology has to be applied to obtain better performance from existing bandwidth, starting with highly congested spectrum areas. Current transmission technology predominantly uses digital binary signals. One technology that provides better bandwidth usage is the application of multi-valued or n-state signals on a much broader scale. Scrambling, descrambling and signal sequence generation is an important element of signal processing technology, especially in wireless communications. Currently, very little technology exists that can perform multi-valued digital scrambling, descrambling and sequence generation. Most of existing solutions in scrambling, descrambling and sequence generation only performs binary functions, as previously discussed.
It is possible to generate non-binary signals with binary switching means, by temporarily transferring non-binary signals or symbols into words or a plurality of binary symbols. This allows the binary signals to be processed by involving fairly standard binary circuitry in novel configurations. After processing the binary signals or symbols one may then transform the binary words or plurality of binary symbols into non-binary symbols. However, there is currently no easy method available to perform n-valued scrambling, descrambling, sequence generation and sequence detection with n-valued technologies that are easy to perform with binary means.
Accordingly, new and improved methods and apparatus for LFSRs to perform n-state scrambling, descrambling, sequence generation and sequence detection on multi-valued or n-state signals with binary technologies are required.